a. IS valid because the parameters are in the correct format. First a string, then a int, then a double.
b. IS NOT VALID because there are no parameters being passed into the method "whatsItDo"
c. IS NOT VALID. although it does pass 3 seperate parameters into the method.. they are not the right type. this is tricky because we may overlook what type the parameters are. but the order and type while passing is important.